#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

// https://learnopengl.com/code_viewer_gh.php?code=includes/learnopengl/shader_m.h
#include <shader_s.h>
// https://learnopengl.com/code_viewer_gh.php?code=includes/learnopengl/camera.h
#include <camera.h>

void InitGLFW();
bool CreateWindow();
bool InitGLAD();

// 窗口大小改变时调用
void framebuffer_size_callback(GLFWwindow *window, int width, int height);
void mouse_callback(GLFWwindow *window, double xposIn, double yposIn);
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);
void processInput(GLFWwindow *window);

// settings 窗口宽高
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

// 相机
Camera camera(glm::vec3(0.0f, 0.0f, 6.0f));
float lastX = static_cast<float>(SCR_WIDTH) / 2.0;
float lastY = static_cast<float>(SCR_HEIGHT) / 2.0;
bool firstMouse = true;

// timing
float deltaTime = 0.0f; // time between current frame and last frame
float lastFrame = 0.0f;

// lighting
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);

GLFWwindow *window;

int main()
{
    InitGLFW(); // 初始化GLFW

    bool isCreated = CreateWindow(); // 创建一个窗口对象
    if (!isCreated)
        return -1;
    bool isGLAD = InitGLAD(); // 初始化GLAD，传入加载系统相关opengl函数指针的函数
    if (!isGLAD)
        return -1;

    // 启用深度测试
    glEnable(GL_DEPTH_TEST);

    // 构建和编译着色程序
    // https://learnopengl.com/code_viewer_gh.php?code=src/2.lighting/2.1.basic_lighting_diffuse/2.1.basic_lighting.vs
    // https://learnopengl.com/code_viewer_gh.php?code=src/2.lighting/2.1.basic_lighting_diffuse/2.1.basic_lighting.fs
    Shader lightingShader("shader/P1_Basic/08_LightModel/basic_lighting.vs", "shader/P1_Basic/08_LightModel/basic_lighting.fs");
    // https://learnopengl.com/code_viewer_gh.php?code=src/2.lighting/2.1.basic_lighting_diffuse/2.1.light_cube.vs
    // https://learnopengl.com/code_viewer_gh.php?code=src/2.lighting/2.1.basic_lighting_diffuse/2.1.light_cube.fs
    Shader lightCubeShader("shader/P1_Basic/08_LightModel/light_cube.vs", "shader/P1_Basic/08_LightModel/light_cube.fs");

    // 设置顶点数据(和缓冲区)并配置顶点属性
    // 1.设置立方体顶点输入  一共需要36个顶点
    float vertices[] = {
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
        0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
        0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
        0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,

        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
        0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,

        -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
        -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
        -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
        -0.5f, -0.5f, 0.5f, -1.0f, 0.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f,

        0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f,

        -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,
        0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,

        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f};
    // 2.设置索引缓冲对象
    unsigned int VBO, cubeVAO;
    glGenVertexArrays(1, &cubeVAO); // 生成一个VAO对象
    glGenBuffers(1, &VBO);          // 生成一个VBO对象

    // 绑定VAO
    glBindBuffer(GL_ARRAY_BUFFER, VBO);                                        // 绑定VBO
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); // 将顶点数据复制到缓冲区中

    glBindVertexArray(cubeVAO);

    // 4.配置位置属性
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *)0);
    glEnableVertexAttribArray(0);
    // normal attribute
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    unsigned int lightCubeVAO;
    glGenVertexArrays(1, &lightCubeVAO);
    glBindVertexArray(lightCubeVAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    // 设置灯立方体的顶点属性指针(仅需要顶点位置数据)
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *)0);
    glEnableVertexAttribArray(0);

    // 循环渲染
    while (!glfwWindowShouldClose(window))
    {

        // 计算帧间隔时间
        float currentFrame = static_cast<float>(glfwGetTime());
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        // 输入
        processInput(window);

        // 渲染
        // 清除颜色缓冲
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        // 清除深度缓冲
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        lightingShader.use();
        lightingShader.setVec3("objectColor", 1.0f, 0.5f, 0.31f);
        lightingShader.setVec3("lightColor", 1.0f, 1.0f, 1.0f);
        lightingShader.setVec3("lightPos", lightPos);
        // 投影矩阵
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), static_cast<float>(SCR_WIDTH) / static_cast<float>(SCR_HEIGHT), 0.1f, 100.0f);
        lightingShader.setMat4("projection", projection);
        // 观察矩阵
        glm::mat4 view = camera.GetViewMatrix();
        lightingShader.setMat4("view", view);
        // 世界坐标变换
        glm::mat4 model = glm::mat4(1.0f);
        lightingShader.setMat4("model", model);
        // 渲染立方体
        glBindVertexArray(cubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

        // 同时 绘制灯光对象
        lightCubeShader.use();
        lightCubeShader.setMat4("projection", projection);
        lightCubeShader.setMat4("view", view);
        model = glm::mat4(1.0f);
        model = glm::translate(model, lightPos);
        model = glm::scale(model, glm::vec3(0.2f)); // a smaller cube
        lightCubeShader.setMat4("model", model);
        // 渲染光照立方体
        glBindVertexArray(lightCubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

        // 检查并调用事件，交换缓冲
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // 可选:一旦资源超出其用途，就取消分配所有资源:
    glDeleteVertexArrays(1, &cubeVAO);
    glDeleteVertexArrays(1, &lightCubeVAO);
    glDeleteBuffers(1, &VBO);

    // 释放/删除之前的分配的所有资源
    glfwTerminate();
    return 0;
}

void InitGLFW()
{
    // 初始化GLFW
    glfwInit();
    // 配置GLFW  第一个参数代表选项的名称，我们可以从很多以GLFW_开头的枚举值中选择；
    // 第二个参数接受一个整型，用来设置这个选项的值。
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    // glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
}
bool CreateWindow()
{
    // 创建一个窗口对象
    window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        // 创建失败，终止程序
        glfwTerminate();
        return false;
    }
    // 将我们窗口的上下文设置为当前线程的主上下文
    glfwMakeContextCurrent(window);
    // 设置窗口大小改变时的回调函数
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    // 设置鼠标移动回调函数
    glfwSetCursorPosCallback(window, mouse_callback);
    // 设置滚轮滚动回调函数
    glfwSetScrollCallback(window, scroll_callback);

    // 隐藏并捕捉鼠标
    // glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    return true;
}
bool InitGLAD()
{
    // 初始化GLAD，传入加载系统相关opengl函数指针的函数
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        // 初始化失败，终止程序
        return false;
    }
    return true;
}

// 窗口大小改变时调用
void framebuffer_size_callback(GLFWwindow *window, int width, int height)
{
    // 设置窗口的维度
    glViewport(0, 0, width, height);
}

// 输入
void processInput(GLFWwindow *window)
{
    // 当用户按下esc键，我们设置window窗口的windowShouldClose属性为true
    // 关闭应用程序
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);

    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
        camera.ProcessKeyboard(FORWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
        camera.ProcessKeyboard(BACKWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
        camera.ProcessKeyboard(LEFT, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
        camera.ProcessKeyboard(RIGHT, deltaTime);
}

// 鼠标移动回调函数
void mouse_callback(GLFWwindow *window, double xposIn, double yposIn)
{
    // 长按T键，鼠标才能控制相机
    if (glfwGetKey(window, GLFW_KEY_T) != GLFW_PRESS)
        return;

    float xpos = static_cast<float>(xposIn);
    float ypos = static_cast<float>(yposIn);

    if (firstMouse)
    {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }

    float xoffset = xpos - lastX;
    float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to top

    lastX = xpos;
    lastY = ypos;

    camera.ProcessMouseMovement(xoffset, yoffset);
}

// 鼠标滚轮滚动回调函数
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset)
{
    camera.ProcessMouseScroll(static_cast<float>(yoffset));
}